Overloading on const and volatile- why does it work by reference?

Question

I have the code:

#include \"stdafx.h\"
#include 

using namespace std;


void func(const int& a)
{
    std::cout << \"func(const)\"         


        

Answer 1

The issue is that the top level const and/or volatile are ignored in overload resolution. So

void foo(const int);

is exactly the same as

void foo(int);

and similarly for volatile. This is a language rule, and it makes sense since the arguments are passed by value. On the other hand, reference to const/volatile or pointer to const/volatile have a different meaning: you are not allowed to call non-const/volatile methods on what they refer to or point to. Here, the const volatile are not top level.

void foo(int& i);       // can modify what i refers to, and this has effects outside of foo.
void foo(const int& i); // cannot modify what i refers to

The two above declarations have very different semantics, so the language makes them distinct concerning overload resolution.